The Frenchman told a news conference at the Indian Grand Prix that Grosjean's confirmation was imminent.
"I think he is on his way to be confirmed soon," he added of a driver who has put last season's wild ways behind him and featured on the podium in his last two races.
Sauber's Hulkenberg and Brazilian Felipe Massa, who is leaving Ferrari to make way for the returning Raikkonen, had been identified as Lotus's top targets but Boullier indicated the choice had narrowed further.
He told the offical formula1.com website that he had recommended to the board of the team that the German be signed.
Lotus also have 2012 GP2 champion Davide Valsecchi as a reserve driver but Boullier indicated the Italian was no more than a last resort.
"Davide is on the list but to bring to the grid next year a driver with no experience is a huge step for them," he declared. "I've done it twice with them, first with (Russian Vitaly) Petrov and then with a semi-rookie Grosjean and I think I've had enough to be honest.
"Davide is on the list because we consider him a good driver, as a GP2 champion, but it's true that if you favour a scenario for next year it will be a driver with experience," added the Frenchman.
"If we cannot find any driver with experience, fitting the strategy of the team, obviously we will go for a rookie driver and then Davide is obviously on the top of the list. It looks harsh, I'm sorry, but it's true."
Boullier has said in the past that Hulkenberg's arrival would depend on the team signing a long-awaited deal with new investors to secure the team's financial future and guarantee the German's wages.